Slide 1

P. Charles (SAAO) T. Shahbaz (IAC) C. Zurita (Obs. San Pedro Martir) R. Hynes (Lousiana State Univ.) D. Steeghs (Harvard-Smithsonian Center for Astroph.) OBSERVATIONAL EVIDENCE FOR STELLAR-MASS BLACK HOLES Jorge Casares (IAC) Slide 2 Impact in Astrophysics Test SNe models and evolution of massive stars e.g. V404 Cyg, GRS 1915+105 1 st observational evidence of BHs not until last 3 decades Fundamental objects throughout astrophysics (XRB, AGN) Stellar-mass BH best opportunity for detailed studies Chemical enrichment of the Galaxy e.g. GRO J1655-40, A0620-00, V4641 Sgr, XTE J1118+480 Accretion physics, outflows and production of VHE radiation e.g. microquasars GRS 1915+105, GRO J1655-40, LS 5039 (:) Slide 3 Outline 1.- Introduction: dynamical evidence 1 st BH candidates in X-ray Binaries From candidates to confirmed black holes 2.- Demography: Population number Masses, distribution and implications 3.- Conclusions Slide 4 Early History 60s: X-ray astronomy (UHURU, Ariel) Population of ~ 10 2 X-ray sources in the Galaxy with L X ~ 10 38 erg/s and variability down to millisec Compact object accreting ~ 10 -9 M /yr from a close companion star (Shklovskii 1967) 1.- Introduction Slide 5 Two types of X-ray binaries 1) High Mass (HMXBs) O-B I L opt /L X 10 2) Low Mass (LMXBs) K-M V L opt /L X 10 -2 Slide 6 Cyg X-1 ( = HDE 226868) O9.7 Iab Velocity K= 64 km/s (latter refined to 75 km/s) and P orb = 5.6 d. Webster & Murdin 1972 Nature 235 37 Bolton 1972 Nature 240 124 Slide 7 The mass function Typically O9.7 Iab has 33 M (and then M X 7 M , i=90) f (M) < M X = 0.25 M Herrero et al. 1995 A&A 297 556 M C =12-19 M M X =4-15 M M C > 10 M i < 65 o M X > 4 M But donor likely undermassive (van den Heuvel & Ostriker 73) Slide 8 EoS of Neutron Stars Oppenheimer & Volkoff (1939): maximum mass for NS stable against gravitional collapse Rhoades & Ruffini (1974): upper limit ~ 3.2 M assuming causality holds beyond nm 3x10 14 g/cm 3. Kalogera & Baym (1996): ~ 2.9 M with EoS accurate ~2 nm Lattimer & Prakash (2004) Slide 9 A 0620-00 ( = N. Mon 75) X-ray Nova discovered by Ariel in 1975 with F x 50 Crabs OUTBURST: Companion 10 3 fainter than X-ray irradiated disc QUIESCENCE: companion dominates optical flux radial velocity studies Slide 10 A 0620-00 ( = N. Mon 75) M x >maximum allowed mass for stable NS P = 7.8 hr K = 4578 km/s f(M)=3.18 0.16 M McClintock & Remillard (1986): First spectroscopic detection of mid-K star Slide 11 Black Hole Candidates Historic debate about existence of BHs (80s) 3 candidates: Cyg X-1 : f (M)=0.25 0.01 M LMC X-3: f (M)=2.3 0.3 M A0620-00: f (M)=3.2 0.2 M Alternative models Multiple stars (Fabian, Pringle, Whelan 1974) Q stars (Bahcall et al. 90) Holy Grail would be f(M) > 5 M (McClintock 86) Slide 12 XRT discovered in 1989 by Ginga with L x 10 39 erg/s V404 Cygni (=GS 2023+338) Casares, Charles & Naylor 1992 Nature 355 614 M x > 6.0 M independently of M C, i f (M)=6.3 0.3 M K0IV donor P = 6.5 d. K= 211 km/s Slide 13 Classic Black Hole candidate based on X-ray properties Quiescence in 2000-01 but companion undetected New outburst in 2002NIII/CIII emission lines at 4630-40 Shahbaz et al. 2001 AAT+NTTVLT GX 339-4: a novel technique NIII/CIII Steeghs & Casares 2002 Sco X-1 HeII Donor not detected but use irradiated lines to trace its orbit Slide 14 GX 339-4 K em =317 10 km/s K 2 f(M) 5.8 0.5 M Black Hole!! (Hynes et al. 2003 ApJ 583 L95) Multigausian fit to NIII lines Determine f (M) in new XRTs during outburst and increase number of BH discoveries. P orb =1.76 d from HeII velocities Slide 15 System Porb f(M) Spect. Type Classification GRS 1915+105 33.5 d 9.5 3.0 M K/MIII Transient V404 Cyg 6.470 d 6.08 0.06 M K0IV,, Cyg X-1 5.600 d 0.244 0.005 M 09.7Iab Persistent LMC X-1 4.229 d 0.14 0.05 M 07III,, XTE J1819-254 2.817 d 2.74 0.04 M B9III Transient GRO J1655-40 2.620 d 2.73 0.09 M F3/5IV,, BW Cir 2.545d 5.75 0.30 M G5IV,, GX 339-4 1.754 d 5.8 0.5 M --,, LMC X-3 1.704 d 2.3 0.3 M B3 V Persistent XTE J1550-564 1.542 d 6.86 0.71 M G8/K8IV Transient 4U 1543-475 1.125 d 0.25 0.01 M A2V,, H1705-250 0.520 d 4.65 0.21 M K3/7V,, GS 1124-684 0.433 d 3.01 0.15 M K3/5V,, XTE J1859+226 0.382 d : 7.4 1.1 M : --,, GS2000+250 0.345 d 5.01 0.12 M K3/7V,, A0620-003 0.325 d 2.72 0.06 M K4V,, XTE J1650-500 0.3205 d 2.73 0.56 M K4V,, GRS 1009-45 0.283 d 3.17 0.12 M K7/M0V,, GRO J0422+32 0.212 d 1.19 0.02 M M2 V,, XTE J1118+480 0.171 d 6.3 0.2 M K5/M0V,, Confirmed Black Holes with dynamical evidence Slide 16 Further support: absence of a hard surface Lack of pulses/X-ray bursts (Remillard et al. 2006) NS BH Quiescent luminosities (Narayan et al. 1997, Menou et al. 1999) Differences in X ray colour-colour diagram (Done & Gierlinski 2003) and Temperatures of the ultrasoft component at high accretion luminosities (e.g. Remillard et al. 2006). Slide 17 BH XRTs are the tip of iceberg of Galactic population 2.- Demography: number, masses How many are there and what is the mass-spectrum ? Dynamical studies of XRTs indicate ~ 75% contain BHs ( f(M)>3 M ) Extrapolation of XRTs since the 60s + assuming outburst duty cycle ~ 10-50 yrs suggest ~ 10 3 dormant BH XRTs (van den Heuvel 93). In good agreement with binary population models (Yungelson et al. 06). Stellar evolution models predict ~ 10 8 (Brown & Bethe 94). Slide 18 Weighing BHs 2) Measure V rot sini 1) 3) Fit ellipsoidal modulation Amplitude is strong function of inclination GRO J1655-40 (Orosz & Bailyn. 97) V404 Cyg (Casares & Charles 93) Slide 19 Typical errors 30% Mass spectrum of BHs 15 reliable masses of BHs: 4-14 M Do BH masses cluster at a particular value? What are the edges of the BH distribution? Is there a continuum distribution between NS & BHs? Goals: improve statistics reduce errors to 10% Slide 20 GRS 1915+105 V404 CYG V404 Cyg/GRS1915+105 BH masses 122 M & 144 M just above mass cut: mass-loss during WR phase overestimated? Comparison with SNIb Models V395 Car (Shahbaz et al. 2004) 4U1700-37/V395 Car/LS 5039 masses of 2.2-5 M : Low mass BHs or massive NSs? LS 5039 (Casares et al. 2005) 4U1700-37 (Clark et al. 2002) Fryer & Kalogera (1999) Slide 21 Conclusions Best observational evidence for stellar-mass BHs based on dynamical studies of X-ray binaries. First BH candidates: Cyg X-1 (1972) & A0620-00 (1986). BH candidates confirmed with discovery of f(M)6 M : V404 Cyg (1992) X-ray properties (lack pulsations/bursts, weak quiescent Lx) supports presence of event horizon. XRTs are best hunting ground for new BHs with 17 cases. Masses range between 414 M . Tip of iceberg of hidden population of ~10 3 BH binaries and ~10 8 stellar-mass BHs in the Galaxy. Better statistics needed to derive constraints to close binary evolution and SNe models. Slide 22 Slide 23 Further support: absence of a hard surface Distinct evolution in colour-colour diagram (Done & Gierlinski 2003) BH Atoll Z-source Cir X-1 Slide 24 Israelian et al. 1999 Nature 401 142: Parecen estrellas normales pero deberan mostrar indicios de un pasado violento (explosin de SN, erupciones de rayos X...) enriquecimiento un factor 6-10 de elementos en la compaera F6III (M C =2.3 M ) Slo se sintetizan en el interior de estrellas > 10 M La compaera fue enriquecida por la explosin de la SN que form el AN en este sistema. XTE J1655-40 Slide 25 Shahbaz et al. 2004 ApJ 493 L39 Jonker et al. 2004 MNRAS 356 621 Firts radial velocity curve (some evidence for irradiation?) M X sin 3 i > 1.9 0.25 M i=70-90 (eclipses) Massive NS or low-mass BH?? X0921-63: ADC with K0III donor in P=9.0 d M x =2.0-4.3 M (no irradiation) M x =1.9-2.9 M (irradiation model) Slide 26 New Technique for dynamical studies Steeghs & Casares 2002 ApJ 568 273 Sharp NIII & CIII Bowen lines in Sco X-1 Doppler shift traces orbit of donor star Allows to measure f(M) in X-ray active Binaries Slide 27 X1822-371 Doppler Tomography K em = 300 8 km/s K M 1 1.14(6) M M 2 0.36(2) M Slide 28 Faint X-ray Binary in quiescence at R=21 VLT + FORS2 at R = 4300 Proving the BH in BW Cir P orb =2.55 days K=279 5 km/s f(M)=5.8 0.3M V rot sin i=71 km/s M c /M X =0.13 Slide 29 V rot sin i=71 km/s q = 0.13 i < 70 o (no eclipses) M X >7.8 M 65 % veiling The latest BH: BW Cir (GS 1354-64) Slide 30 Companion is G0-8: T eff =5100-5700 K and veiled by 65% R 3.6R set by size of Roche lobe L 10 L Radial velocity of Galactic rotation curve =104 km/s, consistent with measured -velocity The latest BH: BW Cir (GS 1354-64) D 27 kpc Furthest BH in the Galaxy! Slide 31 OSIRIS BH Target: XTE J1859+226 Filipenko & Chornock (IAUC 7644) announced f(M)=7.4 1.1 M Requires confirmation!! OSIRIS IN SPECTROSCOPIC MODE AT R~2000- 5000 Zurita et al. 2002 MNRAS 334 999Ellipsoidal modulation at P=7.7 or 9.2 hr R=22.48 0.07 Slide 32 Shahbaz et al. 2004 ApJ 493 L39 Jonker et al. 2004 MNRAS 356 621 Firts radial velocity curve (some evidence for irradiation?) M X sin 3 i > 1.9 0.25 M i=70-90 (eclipses) Massive NS or low-mass BH?? X0921-63: ADC with K0III donor in P=9.0 d M x =2.0-4.3 M (no irradiation) M x =1.9-2.9 M (irradiation model) Slide 33 To learn more about the early epoch see Bradt et al. (1992). The complete story at: http://heasarc.gsfc.nasa.gov/docs/ heasarc/headates/heahistory.html Slide 34 Gallo et al. (2003) found a correlation between radio and X-ray flux for Black Holes in the low/hard state. If the X-rays not beamed, then the Lorentz factors of the compact radio jets should be smaller than 2 to account for the small scattering of the correlation. Slide 35 Why should we expect microquasars to be -ray emitters? Their extragalactic analogous, the quasars, are -ray emitters (analogy quasar-microquasar Mirabel & Rodrguez, Nature 1992,1994 ) Theoretical models predict -rays from microquasars, i.e. Leptonic models: SSC Atoyan & Aharonian 1999, MNRAS 302, 253 Latham et al. 2005, AIP CP745, 323 EC Kaufman Bernad et al. 2002, A&A 385, L10 Georganopoulos et al. 2002, A&A 388, L25 SSC+EC Bosch-Ramon et al. 2004 A&A 417, 1075 Synchrotron jet emission Markoff et al. 2003, A&A 397, 645 Hadronic models: Pion decay Romero et al. 2003, A&A 410, L1 Bosch-Ramon et al. 2005, A&A 432, 609 Slide 36 We have obtained a radial velocity curve of LS 5039 with the INT (IDS) during 2 campaigns on 2002 and 2003 (Casares et al. 2005). The orbital period is found to be 3.906 d and the orbital parameters depend on the spectral lines used in the analysis. All Balmer and He lines included Slide 37 The results suggest that LS 5039 might be a black hole with 3-5 solar masses (Casares et al. 2005) (but optically thin radio spectrum). The orbit is eccentric. Slide 38 Reminder of different error box sizes. Importance of position accuracy from TeV observations. 3EG J1824-1514 3EG J1812-1316 3EG J1826-1302 3EG J1823-1314 GRO J1817-15 -quasar LS 5039 Slide 39 With the new orbital ephemerides (Casares et al. 2005), we have been able to see correlated TeV and X-ray orbital variability: - Accretion changes in an eccentric orbit. - VHE gamma-ray absorption by pair creation with photons of the companion. HESS RXTE Slide 40 We have enough information to build up a Spectral Energy Distribution Slide 41 O6.5V((f)) Inverse Compton Scattering Synchrotron Radiation e-e- e-e- e-e- v jet 0.15c L opt ~ 1 10 39 erg/s -ray, E > 100 MeV, L ~ 4 10 35 erg/s e ~ 10 3 Radio, L 0.1-100 GHz ~ 1 10 31 erg/s X-ray L 3-30 keV ~ 5 10 34 erg/s UV, E ~ 10 eV e-e- e-e- e-e- Proposed scenario Slide 42 We have enough information to build up a Spectral Energy Distribution to extract physical information. A leptonic model with external comptonization can explain the observations (Paredes et al. 2006). Slide 43 Current status on LS 5039: VLA observations covering several orbital cycles reveal no periodic variability, and a progressive cut-off towards high radio frequencies. The source is one order of magnitude brighter than the correlation for BH in the low/hard state. New detailed observations have been conducted with HESS. Results challenging models will be published soon. We are analyzing further VLBI observations to better trace the inner jet structure and eventually measure the jet speed. New models including all angle dependencies (for IC scattering, gamma-ray absorption by photon-photon pair creation, cascading) are being produced, and will hopefully be tested soon against new data (see Dubus 2005, Paredes et al. 2006, Bednarek 2006). Alternative models based on the interaction between the relativistic wind of a non-accreting millisecond pulsar and the UV photons of the massive companion have also been proposed (Dubus 2006).